What makes the “you kiss Ivy’s dad with that mouth?” line so much worse is that I kind of get the sense that Lee does believe Shelby.
From everything we can gather about his and Raelynn’s relationship he was a shitty boyfriend, but we also get a line from him where he reveals that Raelynn told him that Shelby was creeped out by Ivy’s dad. He says it was “in eighth grade or something” and Shelby says that she and Raelynn had that conversation when they were thirteen, so Raelynn presumably told him about this not long after. He remembered that for years, to the point where he “kinda figured that was why she was acting so weird.”* Then, post-reveal, there’s absolutely no indication that he doesn’t believe Shelby. He’s self-interested above all else, still trying to get back together with Raelynn, but he never says he doesn’t believe her. There’s actually more evidence for Mason doubting her allegation.
So that’s why that line stings so much upon every rewatch or reread for me. Not that Mason is innocent of misogyny, but coming from him it would have been a dumb comment he didn’t think through. From Lee, it really feels like he’s trying to hurt Shelby as much as possible.
*The idea that Lee suspected in the moment that Shelby was sleeping with him as a reaction to being sexually abused by an older man (even if, like Nell and Mason, he guessed the wrong one) is very very interesting to me.
